Process of treating certain aluminous abrasives.



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THOMAS ALLEN, 0F NIAGARA FALLS, NEW YORK, ASSIGNOE TO GENERAL ABRASIVE COMPANY, OF NIAGARA. FALLS, NEW YORK.

PROCESS Oil? TREATING CERTAIN ALUMINOUS ABBASIVESL No Drawing.

To all whom it may concern Be it known that I, THOMAS Bones ALLEN, of the city of Niagara Falls, State of New York, United States of America, a subject of the King of Great Britain, have invented a certain new and useful Improved Process of Treating Certain Aluminous Abrasives, of which the following is a specification.

In my pending application No. 22468 I have described a process of forming abrasive materials from bauxite which results in the formation of a mixture of a substantially pure alumina, and an alloy of iron silicon and titanium. Most ofthe alloy settles out, but it is usually found that a certain amount of the alloy remains mixed with the crystalline alumina after solidification- In any subsequent crushing operation this alloy is distributed among the abrasive grains and must be removed if a sufficiently high quality in the abrasive articles made from the material is to be attained.

If the iron in the alloy is over 80% of the whole, it is possible to remove a considerable proportion by means of a magnetic separator, but the separation is not complete, while if less than 80% ofiron be premnt in the alloy the latter is non-magnetic and none of it can be removed by magnetic separation.

It has been proposed therefore to treat the subdivided abrasive by subjecting it to an oxidizing roast which results in the formation of oxids of iron, silicon and titanium, and thereafter chemically treating the roasted material to remove the oxidized impurities, but so far it has not been possible prejudicially affecting the abrasive grain to remove any but the iron oxid leaving behind the oxids of silicon and titanium which, for various reasons, have also a prejudicial efiect on the abrasive. The demand for precision in grinding necessitates not wheel, but demands that when any abrasive article has been found best suited for any given work that it shall always be possible to exactly duplicate the article. Unless the oxids of silicon and titaniumare removed,it is impossible to obtain the desired uniformity in either respect, owing largely to the tendency of the bonding materials employed in forming the abrasive articles to react Specification of Letters Patent.

only uniformity of grain in any individual with the oxids and form weak spots in Patented se at, rare.

Application filed January 27, 1916. Serial No. 74,686.v

the bonding. My aim therefore is to so treat the granular abrasive that all the impurities are converted into a readily removable form.

- According to my process I convert the alloy of iron, silicon and titanium into a ferroso-ferric titano-silicate which is magnetic even with less than 80% of iron in the unchanged alloy. Magnetic separation will thus eliminate most of the compound silicate and any traces remaining can be easily removed by the action of acids such as sulfuric and hydrochloric, or 'salts such as potassium hydrogen, sulfate. if more convenient, the chemical treatment may in some cases be used alone as a substitute for magnetic separation.

The conversion of the alloy into ferrosoferric titano-silicate is most readily efiected in the following manner: I suitably subdivide the crystalline abrasive and mix it with from 3% to 5% of a substance which will readily give up oxygen, such as potassium nitrate. This mixture is then placed in a furnace preferably of the reverberatory type and is subjected to high temperature in an oxidizing atmosphere.

I To obtain the desired chemical reaction I have found that a temperature-of from 1300 to 1500degrees centigrade is necessary. The

material is maintained at this temperature which temperature is probably from 300 to 500 degrees higher than the temperature at which oxidization actively takes lace for from nine to twenty-four hours, ependent on the character of the alloy. After the reaction is completed the material may be treated by magnetic separation and afterward, if necessary, chemically treated as hereinbefore referred to, or in some cases the, chemical treatment substituted for the magnetic separation.

By proceeding in the manner above described I am able to obtain an abrasive essentially free from impurities, and as a result abrasive articles produced therefrom are characterized by greatuniformityof structure and can always be accurately duplicated.

What I. claim as my invention is 1. The process of treating artificially prepared granular aluminous abrasives'containing iron, silicon and titanium as impurities,

which consists in heatin g such abrasive material mixed with an oxygen liberating salt at a temperature sufiicient to convert said impurities into a ferro 5 cate,

2. The process of treating artificially preso-ferric titano-silipared granular aluminous abrasives which consists 1n heating (such abrasive material mixed with an oxygen liberating salt to a grade.

Signed at T of December,

. two undersign Witnesses oronto, Canada, this 24th day 1915, in the presence of the ed Witnesses.

THOMAS .B. ALLEN.

E. P. HALL, L., M LEWIS. 

